Scuba-diving mouthpieces of various kinds have been known and used for many years. The great majority of such mouthpieces are not customized for particular divers; however, some customized scuba-diving mouthpieces have been used or otherwise disclosed. Examples of customized scuba-diving mouthpieces are those shown in U.S. Pat. Nos. 3,107,667 (Moore), 3,844,281, 3,929,548, and 4,136,689 (Shamlian).
Despite advances made in recent years, there are a number of problems and shortcomings with scuba-diving mouthpieces of the prior art, including customized mouthpieces. One problem relates to the mouth fatigue which is fairly common to scuba divers. Mouthpieces are typically held in place by means of the diver's bite on retaining members which project inwardly from a lip-engaging portion to between the diver's upper and lower teeth. This places significant pressures on small portions of the diver's teeth, that is, the portions engaging the retaining members.
Customizing the surfaces of such retaining members to match the tooth surfaces, as in the above-mentioned Shamlian patents, ameliorates the problem to some extent. However, the improvement is quite limited because of the fact that contact with the inwardly-projecting retaining members is limited to only a few teeth.
Greater tooth contact is possible with customized scuba-diving mouthpieces such as that disclosed in the above-mentioned Moore patent. In such patent, the tooth-engaging portions extend well back along the line of molars on either side of the mouth. Such extension provides a greater lever arm, thereby reducing the pressure necessary to hold the mouthpiece in the mouth. Because of this, mouth fatigue should be reduced.
However, the process used to manufacture such mouthpiece is extremely complex, requiring steps such as making wax replicas of the maxillary impression and mandibular impression of the mouth, mounting replicas in relative positions of the partly-opened mouth, carving, uniting tube and tooth impression portions, plaster forming, introducing vulcanizable rubber, separating of plaster from formed rubber, etc.
The complexity of this process rules out quick preparation, such as in a diving equipment shop. Furthermore, it can produce mouthpieces which are less than satisfactory in comfort. In some cases, this is because the relative positions of the relative maxillary and mandibular portions may not be natural. In other cases, this may be because the relative positions are not sufficiently closed. The problem of unnatural jaw position placement is accentuated for the approximately 20% of the population whose jaws are developed well away from normal patterns. In each case, improper relative placement, even in customized scuba-diving mouthpieces, exacerbates the usual problems of jaw fatigue.
Another problem with certain customized scuba-diving mouthpieces of the prior art, particularly those using the diver's teeth to form the final impression on the custom formed portion of the mouthpiece, is that a preliminary heating step is required before forming. This tends to complicate the formation steps and raises a risk of mouth burns, particularly if the process is carried out in a diving shop.
Still another problem with customized scuba-diving mouthpiece formation, particularly in those situations in which the diver's teeth directly form the final impression on the custom formed portion of the mouthpiece, is the unfortunate tendency of some people, during molding procedures, not to bite with their jaws in natural relative positions. In such cases, many people make their lower jaws protrude too far forward, with possible result that the final product will not accommodate the most natural relative jaw positions.
Still another problem with prior customized scuba-diving mouthpieces of the prior art is that such mouthpieces do not very well accommodate what is referred to by divers as "buddy-breathing." Buddy-breathing involves use of a single mouthpiece by more than one diver, as may be necessary when the oxygen supply of one diver is low. In such situations, the mouthpiece is handed back and forth for alternating use by two divers. Customized mouthpieces of the prior art are not well suited for this practice. Indeed, this is particularly true for mouthpieces having extended tooth engagement along either side of the diver's mouth.
There is a clear need for significant improvements in customized scuba-diving mouthpieces.